Proteins are used widely in bio-medical science. For example, antibodies are particularly useful in many diagnostic or therapeutic applications because of their special biological activity and their specific affinity for certain antigenic determinants found on specialized cells in tissue and organs.
The ability to detect the extent to which an antibody has accumulated within certain tissue or organs often depends upon the detection of a label bound to the antibody. Labels which emit radioactivity, fluorescent light under excitation or signals detectible by NMR measurements have been employed.
Although certain metal radioisotopes have been employed as labels, there have been limitations on such use to date. For example, the methods heretofore available for labeling proteins with metal radioisotopes have been of limited utility and have been limited to specific metals. A need has existed, for example, for a better method for labeling antibodies, particularly monoclonal antibodies, with technetium-99m (.sup.99m Tc), a particularly desirable metal radioisotope.